Ultrasonic tool

ABSTRACT

An ultrasonic tool disclosed in a dental instrument embodiment. The tool includes a working tool tip attached to the front of a velocity transformer and a stack of magnetostrictive plates attached to the rear of the velocity transformer. Each magnetostrictive plate is supported solely at its front end, the rear end of each plate being free from connection to either other plates or to any support structures. The water flow through in a continuous axial direction through an axial fluid conduit in the transformer. A spring and hexogonal flange arrangement on the transformer provides multiple radial positioning of the work tool.

United States Paten Carmona et al.

[451 Apr. 4, 1972 [54] ULTRASONIC TOOL [72] Inventors: Delio Carmona; Harvey Diamond;

Joachim Mallga, all of Brooklyn, NY.

[52] U.S. Cl ..3l0/26, 32/58 [51] Int. Cl. [58] Field 01 Search ..32/58, DIG. 4; 310/26 [56] References Cited UNITED STATES PATENTS Haydu ..32/5 8 Kleesattel et al ..32/D1G. 4

3,368,280 2/1968 Freedman et a] ..32/58 Primary Examiner--Robert Peshock Attorney-Ryder, McAuley & Better [57] ABSTRACT An ultrasonic tool disclosed in a dental instrument embodiment. The tool includes a working tool tip attached to the front of a velocity transformer and a stack of magnetostrictive plates attached to the rear of the velocity transformer. Each magnetostrictive plate is supported solely at its front end, the rear end of each plate being free from connection to either other plates or to any support structures. The water flow through in a continuous axial direction through an axial fluid conduit in the transformer. A spring and hexogonal flange arrangement on the transformer provides multiple radial positioning of the work tool.

8 Claims, 7 Drawing Figures Patented April 4, 1972 2 Sheets-Sheet 72 5 INVENTOR.

JOACHIM MALIGA BY HARVEY DIAMOND DELIO CARMONA ULTRASONIC TOOL This invention relates in general to an ultrasonic tool and more particularly to an ultrasonic tool having a design that provides improved efficiency, noise and handling characteristics.

BACKGROUND OF THE INVENTION There are known ultrasonic tools, such as dental instruments, which employ a working tool, velocity transformer and stack of magnetostrictive plates in combination to provide a transducing of electrical power to mechanical power. The major limitations on the known ultrasonic tools of this type arise from efficiency limitations. Heat and noise are produced in addition to magnetostrictive movement. The heat requires cooling fluid and the noise is obviously undesirable. But improved efficiency is of major importance in order to obtain as much mechanical energy output as is possible for a given electrical energy input.

Accordingly, it is a major purpose of this invention to provide a design that will have improved efficiency characteristics. It is a further related purpose of this invention to provide an ultrasonic tool design which will generate less heat and less noise than hitherto has been the case for a given mechanical energy output.

The cooling fluids employed range from ordinary tap water to dentifrice slurries and other abrasive slurries. Depending on the amount and nature of slurry required, there have been a range of problems relating to the tendency of the slurry to clog small conduits or for slurry particles to become caught between the plates of the magnetostrictive stack.

Accordingly, it is a further object of this invention to provide a design that will minimize or eliminate the tendency of the slurry particles, or of other particles in the cooling water, to clog the conduit or stack of magnetostrictive plates.

It is a further related object of this invention to provide a design which will allow varying densities of slurry fluids to be used within the instrument.

In order to provide adaptability of the ultrasonic tool, it is still another object of this invention to provide an improved tool positioning arrangement whereby the operator, in a simple fashion, can change the radial position of the tool within the instrument.

BRIEF DESCRIPTION OF THE INVENTION Briefly, one embodiment of this invention is an improvement in an ultrasonic dental tool which has the usual combination of a tool at the forward end of the instrument, a velocity transformer connected to and rearward of the tool, a stack of magnetostrictive plates connected to and rearward of the velocity transformer. The magnetostrictive stack is energized by an electomagnetic field established by an electrical coil wound on a bobbin which surrounds the magnetostrictive stack.

The improvement of this invention includes a magnetostrictive stack design in which the individual plates are connected to one another solely at their front ends. Thus the stack is open at its rear end and each plate vibrates substantially independently of the other plates. As a result there is improved efficiency and less noise. There is a straight axial fluid conduit within the velocity transformer. Clean cool fluid introduced at the rear end of the dental instrument 'will flow over and through the magnetostrictive stack, into and through the straight axial conduit within the velocity transformer and finally out onto or adjacent to the work tool which is held b the velocity transformer.

The cooling fluid is readily able to flow through the stack. Particles that otherwise might tend to be caught in the stack will be worked free as the stack vibrates in use because the individual layers of the stack are free to move relative to one another.

The straight substantially axial flow of cooling fluid through the instrument provides a design whose radial symmetry minimizes not only the cost of production but also minimizes the discontinuities which cause a loss of the vibratory energy being transferred forward from the magnetostrictive stack. Though it is not certain, as to the exact reasons why the straight axial conduit enhances performance, it is believed that one major reason relates to the cavitation of the cooling fluid. By avoiding turns in the path of the fluid, it is believed that a more efficient cavitation of the fluid is provided.

The velocity transfonner itself is positioned within the bobbin by an O-ring. The O-ring is mounted on the transformer at an axial position that is near the node of the vibratory motion of the transformer. This O-ring forms a fluid-tight seal and protects the energizing electric coil wound on the outside of the bobbin from contact with fluid.

The cooling fluid is applied to the instrument by a fluid supply hose which is clamped onto an inlet conduit at the rear of the bobbin so as to provide a fluid-tight seal and thus further serve to prevent fluid from leaking out and coming into contact with the energizing coil.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and purposes of this invention will become apparent from the following detailed description and drawings, in which all of the figures are various views of the same embodiment.

FIG. 1 is a longitudinal sectional view, in partial elevation, of an ultrasonic dental instrument embodying this invention;

FIG. 2 is a longitudinal view, in elevation, of the bobbin and of certain other interior elements of the FIG. 1 device;

FIG. 3 is a longitudinal sectional view of the housing of the FIG. 1 instrument;

FIG. 4 is a longitudinal view, in elevation, of the FIG. 1 device;

FIG. 5 is an exploded longitudinal view, in partial section, of the FIG. 1 device, illustrating various parts in assembly;

FIG. 6 is a longitudinal sectional view of the zone where the velocity transformer and magnetostrictive stack are joined together; and

FIG. 7 is a perspective view of the rear end of the stack.

DESCRIPTION OF A PREFERRED EMBODIMENT This ultrasonic tool invention is described in detail in an embodiment designed for use as a dental tool. However, the basic tool, primarily the stack of magnetostricture plates and transformer, may be employed in a wide variety of instruments to perform functions such as impart grinding, engraving, polishing, cutting, joining, cleaning and drilling.

The major structural elements of the ultrasonic dental instrument 10 shown in the drawings include a two piece housing. The housing is composed of a rearward tubular section 12 and a forward section 14. These two sections 12 and 14 of the housing are threaded together and thus form the housing 10 in which only a single interface line 10a (see FIG. 4) appears on the outer surface of the instrument 10. This design thus minimizes the number of areas which may trap dirt and accordingly improves the appearance of the instrument.

A bobbin 16 is mounted within the tubular portion 12 of the housing. This bobbin 16 has a forward flange 18 which flange is square in cross section and serves to position the bobbin 16 within the housing section 12. Flange l8 abuts against a shoulder 12s in the housing portion 12 and thus the axial position of the bobbin 16 is determined. The interior surface 12a of the housing portion 12 that is adjacent to the flange 18 is also square in cross section so that the flange 18 is prevented from rotating within the housing portion 12. In this fashion, the bobbin 16 as well as all the parts mounted on the bobbin 16 are prevented from radial rotation within the housing 10.

A stack of magnetostrictive plates 22 is connected at its forward end to the rear end of the velocity transformer 24. A dental tool tip 26 is threaded onto the front end of the velocity transformer 24. Thus a three element 22, 24, 26 vibratory unit is provided.

The magnetostrictive stack 22 and the rear portion of the velocity transformer 24 are longitudinally mounted within the bobbin 16. A flange 28 (see FIGS. 1 and S) on the velocity transformer 24 is hexagonal in cross section. This flange 28 is held against rotational movement by a bobbin inner surface area 16a that is hexagonal in cross section. The hexagonal flange 28 has a slip fit relationship with the hexagonal area 16a so that the velocity transformer 24 and associated magnetostrictive stack 22, will be held in axial alignment within the bobbin 16 and also so that the transformer 24 and stack 22 can readily be withdrawn in whole, or in part, from within the bobbin 16. Because of this hexagonal flange 28 on the transformer 24 part of the vibratory unit, it becomes possible to exert appreciable oblique force on the working tool tip 26 without having the tool tip rotate out of a desired position.

A sealing O-ring 30 is mounted in an annular groove in the transformer 24 to seal water into the cavity behind the O-ring 30 except as such water flows out through the central opening 32.

A spring 34 in slight compression is wound on a shank portion of the velocity transformer 24 and is held in compression between a rear face of the housing section 14 and the forwardly facing surface of the hexagonal flange 28. Thus pressure is exerted to hold the hexagonal flange 28 against the shoulder 16s which in turn holds the bobbin 16 back and presses the bobbin flange 18 against the housing shoulder 12s.

A current carrying coil of wire 36 is wound on the outer surface of the bobbin l6 and is connected through the rear of the instrument to a source of exciting current which may be a series of pulses having a frequency equal to that at which it is desired to excite the stack of magnetostrictive plates 22.

As shown in FIG. 6, the front end of the stack 22 has a threaded projection permitting it to be screwed into a threaded recess at the rear of the velocity transformer 24. This permits rearly replacement of damaged or worn stacks 22. By contrast the rear end of the stack 22 is allowed to hang free in a cantilever fashion. Moreover, each magnetostrictive plate 22p in the magnetostrictive stack 22 has a free rear end (see FIG. 7) and is not connected at its rear end to any other plate in the magnetostrictive stack nor to any other part of the instrument. As a result, each plate 22p in the magnetostrictive stack 22 is free to expand and contract in a longitudinal direction in accordance with its own performance parameters. This means that the individual plates do not dampen one another. This stack design featuring individual plates 22p each one of which is supported solely at its front end provides enhanced efficiency of operation. For a given power input the result is less noise and less heat generation than with other known stack designs. Thus a greater proportion of the input electrical power is transformed into mechanical energy available at the tool tip 26. In operation it is believed that the flowing water tends to float the individual plates apart from one another to enhance the independent operation of each plate. Because the plates operate independently of one another, they do not dampen one another.

it is believed that one of the reasons this open stack design generates less noise, than if the plates 22p were connected together at their rear, is that the plates 22p do not slap one another when vibrating.

When slurry is used, as it is in a dental tool and in other grinding tools, the fact that the plates 22;; are unconnected (except at their front ends) means that the abrasive particles tend to remain free from being caught between the plates. This feature not only increases efiiciency but extends the life of the plates.

Since improved efficiency is a major purpose of this design, it is preferable to enhance efficiency by using a magnetostrictive material having as high a resistivity as feasible. A very pure ballast nickel has been found to be a desirable material for the plates 22;).

With the above structure in mind, various additional structural and operational features can be understood.

With respect to the forward portion of the instrument, it should be noted that the work tool 26 is replaceable. The tool 26 might be any one of a number of types of dental tools but can be considered for present purposes to be a tooth cleaning instrument. It is screwed into the shank portion of the transformer 24. The shank portion of the transformer 24 in turn, extends through an axial bore in the forward section 14 of the housing. To remove and replace the work tool 26 simply requires that the dentist hold the tubular section 12 in one hand and with an appropriate wrench engage the flats 38 on the work tool 26. The work tool 26 can then readily be unscrewed for removal or screwed on for use. Because the hexagonal flange 28 holds the transformer 24 from rotation within the bobbin 16 and because the square flange 18 holds the bobbin from rotation within the housing 12, it becomes possible for the dentist to simply hold the housing 12 and with a single wrench remove or screw in a work tool 26.

'The hexagonal flange portion 28 of the velocity transformer 24 in combination with the slip fit mounting in the hexagonal wall area 1611 of the bobbin makes it possible to position the tool 26 in any one of six different radial attitudes. This becomes important because the tubing and wiring that extend out the rear of the instrument l0 exert a rotational torque on the instrument 10 to cause the instrument 10 to tend to a particular radial attitude at which the torque is minimized. lt is undesirable for the dentist to have to fight this torque. The design described, permits him to position the work tool 26 in a radial position that minimizes the torque so exerted on the instrument 10. To change the radial positioning of the work tool 26, all that is required is that the work tool 26 be pulled forward, compressing the spring 34, and rotated to a new position. The spring 34 will then hold the work tool in the new radial position. In industrial applications, this ability to radi ally shift the working tip makes possible the permanent mounting of the housing while providing adjustability for the angle of the working tip.

vIn addition it is an important feature of this design that the hexagonal transformer flange 28 in combination with the square bobbin flange 18 prevents rotation of the working tip 26 when the tip 26 is subjected to torque in use.

To provide further protection of the coils 36 from fluid, a resilient O-ring 40 is mounted in a groove near the forward portion of the bobbin 16 so that when the bobbin 16 is mounted in the tubular housing portion 12, the O-ring 40 is squeezed between the bobbin l6 and housing 12 to effect a water-tight seal.

The energizing coil 36 (which may best be seen in FIG. 2) is wound along the length of the bobbin l6 and is energized through leads 42 which extend out the rear of the instrument.

FIG. 2 further indicates the sealing mechanism which is employed at the rear of the instrument 10. A shank portion 44 of the bobbin 16 is threaded to engage a rear end sealing cap 46. As the rear cap 46 is screwed onto the shank portion 44 of the bobbin 16, cone-like portions of the shank 44 and rear cap 46 are brought together to compress between them a flexible water inlet tube 48. Thus a positive seal is provided so that water, or other liquid or slurry, can flow into the instrument through the tube 48, through an axial bore in the shank 44, into the interior of the bobbin through and around the stack 22 and finally through a straight axial bore extending throughout the transformer 24 into and/or onto the work too] 26.

This positive sealing arrangement at the rear of the instrument 10 in conjunction with the sealing provided by the 0- rings 30 and 40 provides an important safety feature in keeping the coil 36 free from water.

The radial symmetry of the instrument structure results in a general simplicity of manufacture and ease of assembly. Perhaps more importantly, the radially symmetric design of the velocity transformer 24 results in an efiiciency in the transmission of vibratory motion that aids in minimizing losses through heat. Further efficiency and minimization of heat losses arise through the elimination of mass and the elimination of damping at the rear end of the stack 22.

The structure of the stack 22 without a binding mass also enhances the production and operation of the instrument as less precise tuning is required to obtain close to optimum efficiency.

Although this invention has been described with one preferred embodiment, it should be obvious that certain changes can be made in the invention as described without departing from the spirit and scope of the invention.

What is claimed is:

1. In an ultrasonic tool having a housing within which there is disposed an energizing coil wound on a bobbin, a stack of magnetostrictive plates disposed within the bobbin, and a velocity transformer connected to and extending forward from the stack of magnetostrictive plates, the improvement comprising:

each of said magnetostrictive plates of said stack being supported solely at its forward end, the rear end of eachof said plates hanging free from connection to any other of said plates in said stack and free from connection to any support structure.

2. Improvement of claim 1 further comprising:

an axial conduit for carrying cooling fluid, said axial conduit extending axially through said velocity transformer from the juncture between said transformer and said stack of magnetostrictive plates to the forward end of said transformer.

3. The ultrasonic dental tool improvement of claim 1 further comprising:

a multi-faceted annular flange on said velocity transformer,

a multi-faceted inner surface of said bobbin positioned to engage the faces of said flange and to hold said flange and thus said transformer from rotational movement within said bobbin,

said flange having a slip fit relationship to said multi-faceted surface of said bobbin to permit axial withdrawal of said flange from said bobbin,

spring means to normally hold said flange within said bobbin in a position where the faces of said flange engage the faces of said inner surface of said bobbin, said spring means being compressible to permit withdrawal of said flange from engagement with said faces of said bobbin so that said transformer may be rotated to different radial positions within said bobbin.

4. Improvement of claim 3 further comprising:

an axial conduit for carrying cooling fluid, said axial conduit extending axially through said velocity transformer from the juncture between said transformer and said stack of magnetostrictive plates to the forward end of said transformer.

5. The improvement of claim 1 further comprising a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack.

6. The improvement of claim 2 further comprising:

a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack.

7. The improvement of claim 3 further comprising:

a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack.

8. The improvement of claim 4 further comprising:

a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack. 

1. In an ultrasonic tool having a housing within which there is disposed an energizing coil wound on a bobbin, a stack of magnetostrictive plates disposed within the bobbin, and a velocity transformer connected to and extending forward from the stack of magnetostrictive plates, the improvement comprising: each of said magnetostrictive plates of said stack being supported solely at its forward end, the rear end of each of said plates hanging free from connection to any other of said plates in said stack and free from connection to any support structure.
 2. Improvement of claim 1 further comprising: an axial conduit for carrying cooling fluid, said axial conduit extending axially through said velocity transformer from the juncture between said transformer and said stack of magnetostrictive plates to the forward end of said transformer.
 3. The ultrasonic dental tool improvement of claim 1 further comprising: a multi-faceted annular flange on said velocity transformer, a multi-faceted inner surface of said bobbin positioned to engage the faces of said flange and to hold said flange and thus said transformer from rotational movement within said bobbin, said flange having a slip fit relationship to said multi-faceted surface of said bobbin to permit axial withdrawal of said flange from said bobbin, spring means to normally hold said flange within said bobbin in a position where the faces of said flange engage the faces of said inner surface of said bobbin, said spring means being compressible to permit withdrawal of said flange from engagement with said faces of said bobbin so that said transformer may be rotated to different radial positions within said bobbin.
 4. Improvement of claim 3 further comprising: an axial conduit for carrying cooling fluid, said axial conduit extending axially through said velocity transformer from the juncture between said transformer and said stack of magnetostrictive plateS to the forward end of said transformer.
 5. The improvement of claim 1 further comprising: a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack.
 6. The improvement of claim 2 further comprising: a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack.
 7. The improvement of claim 3 further comprising: a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack.
 8. The improvement of claim 4 further comprising: a screw and socket connection between said velocity transformer and said stack to provide for disengagement and replacement of said stack. 